Field
The present disclosure relates generally to intelligent electronic devices (IEDs) and, in particular, to an intelligent electronic device and method thereof for preventing loss of data on a loss of power to the intelligent electronic device.
Description of the Related Art
Monitoring of electrical energy by consumers and providers of electric power is a fundamental function within any electric power distribution system. Electrical energy may be monitored for purposes of usage, equipment performance and power quality. Electrical parameters that may be monitored include volts, amps, watts, vars, power factor, harmonics, kilowatt hours, kilovar hours and any other power related measurement parameters. Typically, measurement of the voltage and current at a location within the electric power distribution system may be used to determine the electrical parameters for electrical energy flowing through that location.
Devices that perform monitoring of electrical energy may be electromechanical devices, such as, for example, a residential billing meter or may be an intelligent electronic device (“IED”). Intelligent electronic devices typically include some form of a processor. In general, the processor is capable of using the measured voltage and current to derive the measurement parameters. The processor operates based on a software configuration. A typical consumer or supplier of electrical energy may have many intelligent electronic devices installed and operating throughout their operations. IEDs may be positioned along the supplier's distribution path or within a customer's internal distribution system. IEDs include revenue electric watt-hour meters, protection relays, programmable logic controllers, remote terminal units, fault recorders and other devices used to monitor and/or control electrical power distribution and consumption. IEDs are widely available that make use of memory and microprocessors to provide increased versatility and additional functionality. Such functionality includes the ability to communicate with remote computing systems, either via a direct connection, e.g., a modem, a wireless connection or a network. IEDs also include legacy mechanical or electromechanical devices that have been retrofitted with appropriate hardware and/or software allowing integration with the power management system.
Electronic devices, including power metering devices, have the need to record information that is retained when the device loses main power. The operating program, configuration data and collected information, all have a need to be maintained by the device. EEPROMs; battery-backed RAMs or NVRAMs; and FLASH have been commonly used for this purpose, with various pros and cons.
Historically, EEPROMs have been extensively used for non-volatile memory storage; that is, they retain information when the device has no power. EEPROM stands for Electronically Erasable Programmable Read-Only Memory. EEPROMs come in many sizes, but typically are used for smaller memory applications. By using floating-gate arrays, EEPROMS can store on or off states, 0 or 1 values, by either draining or storing electrons in the floating gates; Once stored, power need not be maintained to the gates to retain the states. With an EEPROM, any byte can be changed at any time, independent of the values of the other bytes; however, it typically takes a longer time to change a byte in an EEPROM than it takes for a microprocessor to send the command to the EEPROM to write the byte. Many EEPROMs allow multi-byte writes, allowing the microprocessor to provide without delay a short sequence of bytes to be written, with an increase both in the delay before the new values are written and in the delay before additional bytes may be written.
Battery-backed RAMs or NVRAMs (which stand for Non-Volatile Random Access Memory) are another option for non-volatile memory storage. These are regular RAM devices, that would ordinarily lose stored information if the device loses power, but rather than relying exclusively on system power, these devices will alternately be powered by a battery, either separately or, in the case of NVRAMs, as part of the device itself. As RAM devices, they typically operate without delays. While typically larger than EEPROMs in terms of memory size, because they still require power to maintain their memory states when there is no system power, there tend to be limits on the usable size of Battery-backed RAMs or NVRAMs in a system. As well, because they are drawing power from the battery to maintain the memory state when system power is not available, the usefulness of the NVRAM is limited by the capacity of the battery used. Plus, in terms of physical size (as well as cost), the use of batteries increases the size of the necessary components, and could require design considerations if the need to replace batteries is important.
In recent times, FLASH memory has seen a rise in use in many applications. FLASH is not an acronym, instead the word ‘flash’ is used because the erasure of large pages of memory was originally described as being like the flash of a camera. FLASH memory is similar to EEPROMs, in that there are delays in the process of changing information stored on a FLASH. With EEPROMs, writing to a byte internally involves first erasing the byte to clear the old pattern, followed by writing the new pattern; with FLASH, erasing is a separate external step, performed on a page of bytes all at once, which can then be followed by writing new patterns. Rather than allowing individual byte or small group modifications with moderate delays, FLASH organizes memory into large sectors. Erasing a sector at a time requires a large delay (but usually shorter than the sum of the internal times it takes to erase/clear equivalent numbers of bytes in EEPROMs), while writing bytes to a sector involve individual delays smaller than those typical for writing bytes to an EEPROM.
Therefore, a need exists for techniques for saving data on a power loss to prevent loss of data while overcoming the above-described disadvantages.